Systems that deliver a controlled flow of liquid are well known in the art—such as Intra Vessel Infusion poles and kits. The rate of infusion is typically monitored by the naked eye as the liquid passes through a transparent control compartment where the liquid drips in visible droplets. As the size of the droplet is relatively fixed and determined by the chemical properties of the liquid, the rate of droplets is a good estimate of the flow and can be easily monitored by the care giver's eye.
However, monitoring the rate of the droplets requires continuous attention by a human operator or by the patient.
Several solutions have been suggested to automate the monitoring of the droplet rate. Some solutions involve a controlled electric pump (such as the “Sabratek 3030 IV Infusion Pump” made by Baxter from Chicago, II) that is very accurate. However, it is costly and too cumbersome for field emergency treatment. Furthermore, it is out of the scope of the present invention.
Some solutions have also been suggested as an add-on on conventional IV infusion sets, such as IVIC by HanvitMD from Korea. It is a special watch that enables an operator to precisely set the drop rate. This product does is not attached to the IV system and does not free the operator from having to attend to it.
Another solution is described in U.S. Pat. No. 4,504,263 to Steuer et al., where the line of sight between a light source and a light sensor is blocked by the droplets and the rate of droplets falling can be determined from the electric signal of the sensor. This solution is good only for vertical orientation of the device and consumes significant electric power, because the circuitry must be active at all times.
Other solutions, such as described in U.S. Pat. No. 7,190,275 to Goldberg et al., U.S. Pat. No. 4,509,943 to Hanzawa, U.S. Pat. No. 4,432,761 to Dawe, and in other publications teach a light beam crossing mechanism where the falling droplet crosses the line of sight between a light source and a light sensor. They too suffer from similar problems: they consume electricity continuously and they are sensitive to the vertical orientation of the control compartment.
Thus, it would be very desirable to have a drip monitoring system that is not sensitive to the vertical orientation of the control compartment and that does not consume power very frequently.
It is the purpose of the present invention to provide such a solution,